why distinctions within XHTML?

[Hunter, David]

From: Mark Birbeck [mailto:Mark.Birbeck at iedigital.net]
Sent: Wednesday, September 01, 1999 2:30 PM> To: XML-Dev Mailing list
> 
> In the context of my last email, by 'intermediary', I meant conduit,
> rather than evolutionary stage. Just as you might convert XML 
> to 'XSLFO'
> and then convert it to postscript or HTML, so you might go
> HTML->XHTML->FliXML.
> 
> You seem to think I mean that HTML and its variants will 
> disappear, and
> that instead, XML will be used everywhere with CSS or something to
> display it. Actually I don't, but I think it will eventually 
> only exist
> as fragments in stylesheets that are applied to XML, and very small
> devices that have not got an XML parser, but have got parsers for
> various XHTML modules.

[rest of email snipped, in which Mark points out some good uses for XHTML,
and points out a glaring error on my part, where I stated that XHTML isn't
about transforming other XML vocabularies into XHTML, when this is obviously
one of its likely uses.  Ahem.  :-) ]

Yes, I did in fact misinterpret your last [couple of?] emails as saying that
XHTML would disappear in favour of XML+CSS, or some other formatting
technologies.  And I love the idea of being able to embed XHTML fragments
into other XML vocabularies, such as

<order>
  <customer>Fred Jones</customer>
  <comments xmlns="xhtml-namespace">
    <p>Bought <em>500</em> units!</p>
  </comments>
</order>

I can even see the utility of transforming from HTML to XHTML to other XML
vocabularies in many circumstances.  (Such as cases where you want to use
XSL to go from the XHTML to the other vocabulary, since XSL needs XML as
input.)

What I don't see is why any of this means that we need to distinguish the
three flavours of XHTML with separate namespaces.  <aside>As to why we need
separate flavours of XHTML in the first place, I'll go with the explanation
given by Ann Navarro in an earlier email, that XHTML *1* is just meant to
just put HTML 4 into XML syntax, and that *future* versions may or may not
combine them.  This works for me, since I happen to like the versioned
approach.</aside>

Using three namespaces conceptually makes XHTML three distinct languages,
instead of one language that can be used in three ways.  I'm hoping very
much that the W3C will eventually bring XHTML back to one flavour, instead
of three.  Eventually, I would like to be able to just do what I've done
above, and say "this is XHTML", without having to specify that "this is
XHTML, and it's strict" etc.  I'm worried that if the three current flavours
are distinguished by namespaces, it makes it much harder to bring them all
back to one eventually, but that instead there will always be a strict, and
a loose, and a frameset.

On the other hand, if the three flavours are distinguished by an attribute,
or a processing instruction, then they can just come up with *one* XHTML
namespace, which can be used from now on whenever someone needs to author
XHTML.

In other words, any application which is working with XML can just look for
that namespace and say "oh, this element is using XHTML.  I'll hand it off
to the XHTML application to process".  If we use separate namespaces, then
any application which may have XHTML to process will have to know about all
of those namespaces.  Perhaps not a big deal, if only those three namespaces
are ever used, but perhaps a huge deal if more flavours of XHTML are
created, or the namespaces are versioned.  (That is, a namespace for
XHTML-strict-1.0, and one for XHTML-strict-1.1...)  Now, instead of just
being able to mix XHTML into my documents and not worry about it, my
application needs to look for a number of namespaces which could denote
XHTML, and be updated any time new XHTML namespaces are introduced.

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